Respuesta :
The answer is A because the vaccine only affects the susceptible host therefore the chain can only be broken once it reaches them.
Answer: A. At the susceptible host
Explanation: For a person to become infected with a pathogen, he or she must be a susceptible host. A susceptible host is someone who is able to contract the pathogen. Vaccines can help break this link in the chain of infection, therefore making a person not susceptible. Susceptibility of a person depends on several factors:
* The number and species of pathogen
* The duration of exposure to the pathogen
* The host’s overall general physical condition
* The host’s psychological health status
* The host’s occupational or lifestyle environment
* The presence of underlying diseases or conditions in the host
* Age of the host... PF